Queensland Silver Wattle Acacia podalyriifolia A.Cunn. ex G.Don
Synonyms - Racosperma podalyriifolium
Family: - Mimosaceae
Names:
Acacia was the name of a thorny Egyptian tree.
Podalyriifolia because its foliage resembles that of Podalyria.
Wattle comes from British settlers making wattle and daub buildings using Callicoma serratifolia branches which was then called Black Wattle and is similar to the other Acacias of the area.
Queensland Silver Wattle because it is native to Queensland, its foliage is silvery and it is a member of the Wattle or Acacia genus.
Other Names:
Mount Morgan Wattle.
Summary:
Queensland Silver Wattle (Acacia podalyriifolia) is a bushy shrub or small tree 2-7 m high with grey smooth to finely fissured bark, branchlets which are white and usually velvety-hairy and silvery foliage. The leaves are replaced with broad undivided leaf-like phyllodes that are 10-40 mm long by 10-25 mm wide, with wavy margins, usually hairy and each face with 1 prominent longitudinal vein (a non-central midrib). The golden globular flower heads are arranged in 10 to 20-headed sprays each head with 15-30 flowers. The seed pods are brown with a white bloom, often velvety-hairy, up to 12 cm long by 10-20 mm wide, flat and often slightly twisted or wavy.
Native to New South Wales and Queensland, it was widely planted as an ornamental and is now a weed of roadsides and disturbed woodland often near settlement and refuse disposal areas. It flowers from May to July.
Description:
Cotyledons:
Two.
First leaves:
Bipinnate.
Leaves:
Alternate. On mature plants there are no true leave and only green leaf like phyllodes which are flattened petioles.
Phyllodes: Usually blue-green with a whitish bloom but sometimes green, broadly egg shaped to elliptic, (10)20-40(50) mm long by 10-20(27) mm wide, straight or somewhat curved. Mid vein prominent and off centre. Lateral veins, feather-like and faint to conspicuous. Tip pointed to round with a fine, hooked point (mucro). Sides curved to wavy, base tapering and symmetric. Initially very hairy but may become hairless with age apart from hairs on the edges. No glands or 1 or 2 inconspicuous small glands on the edges in the lower half of the phyllode.
Stipules - Present
Petiole - Base of petiole swollen to form the pulvinus. The pulvinus is 1-2 mm long and hairy.
Blade - None on mature trees, bipinnate on juvenile foliage.
Stems:
2-7 m tall often widely spreading.
Young twigs are whitish and somewhat hairy.
Branchlets somewhat circular in cross section and velvety hairy with a silvery bloom. Very rarely the branchlets are hairless.
Bark - Grey and smooth or finely fissured.
Flower head:
Globular, fragrant flower heads, 6-8 mm diameter with 15-30 golden yellow flowers. 10-20 heads on an extended axillary inflorescence (raceme) that is 30-110 mm long that is velvety hairy. Flower head stalks (peduncles) (3)5-10 mm long and hairy.
Flowers subtended by a small bracteole.
Flowers:
Fragrant. Bisexual. Actinomorphic.
Ovary - Superior. One carpel. Hairy. Numerous ovules
Style - Threadlike
Calyx - 5 short lobes with stiff white hairs. Sepals united.
Petals - 5. Hairy.
Stamens - Numerous and free.
Anthers - Fertile. 2 celled. Opening by longitudinal slits
Fruit:
Straight or twisted, flat, oblong, somewhat leathery pod, 50-90(120) mm long by 10-20 mm wide and often with undulating edges. Pods brown with a silvery-white bloom and usually hairy when young and may become hairless with age. Seeds arranged longitudinally in the pod.
Opens by two valves and spills it seed to one side (unilaterally dehiscent)
Seeds:
Dull black and oblong, 6-7.5 mm long
Seed stalk (funicle) thread like, short and expanded (arilate) toward the seed.
Roots:
Taproot.
Key Characters:
Mature leaves reduced to phyllodes
Phyllodes without pungent apex
Phyllodes with distinct mid vein and conspicuous lateral veins
Phyllodes <2.5 times as long as broad and less than 45 mm long.
Branchlets ± terete
Racemes usually axillary
10-20 flower heads per raceme
Flower heads globose
Flowers actinomorphic.
Ovary superior.
Stamens all free, more than 10 and usually < 0.5 mm long, white cream, yellow or orange yellow
Adapted from J.R. Wheeler, G. Harden.
Biology:
Life cycle:
Perennial. Fast growing and short lived (about 20 years).
Physiology:
Reproduction:
By seed.
Flowering times:
May to July in WA.
Mainly June to July in Queensland in it native habitat.
Any time of the year in NSW.
Late winter to early spring in SE Australia.
Seed Biology and Germination:
Vegetative Propagules:
Hybrids:
Allelopathy:
Population Dynamics and Dispersal:
Long distance spread is usually by intentional planting. Medium distance spread is from dumping of garden waste. Local spread is probably due to birds.
Origin and History:
Native to Queensland and possibly northern NSW close to the Queensland border.
Widely planted as an ornamental tree and has subsequently escaped and naturalised in SA, WA and NSW.
First collected by A. Cunningham in 1929 in the Birnam Range of the Brisbane River valley in Queensland.
Distribution:
NSW, QLD, SA, WA.
Naturalised in South Australia, Western Australia and the Sydney region.
Invasive in the Blue Mountains in NSW.
Jarrah Forest, Swan Coastal Plain and Warren regions in WA.
Courtesy Australia's Virtual Herbarium.
Habitats:
Eucalypt woodlands.
Naturalised in a wide range of habitats.
Climate:
Cool temperate, Mediterranean.
Soil:
Grey sand, lateritic loam. Soils derived from sandstones and granites.
Naturalised on a wide range of soils.
Plant Associations:
Eucalypts.
Significance:
Beneficial:
Ornamental. gums, pollen.
Detrimental:
Environmental weed spreading along roadsides and into bushland.
One of the more invasive Acacias.
Toxicity:
Not recorded as toxic
Symptoms:
Treatment:
Legislation:
None.
Management and Control:
Picloram, Garlon and glyphosate are used for chemical control as overall sprays, cut stump or topical application to the trunk.
Use Garlon 480 at 1:400 and Roundup CT at 1:200 as an overall spray for control of juvenile shrubs and 2 L/ha Garlon 480 for control of seedlings.
2 L/ha of Roundup (360 g/L) controls seedlings in autumn winter and spring but 4 L/ha was required for late summer applications.
Fire destroys the mature shrubs but usually leads to a mass germination of seedlings. However if these seedlings are controlled it very quickly reduces the seed bank in the soil. Seedlings tend not establish in mature stands.
A long term control plan is usually required for success.
Target areas that have been recently burnt because these will be more prone to invasion and the seed bank will be reduced due to the fire induced germination of seed.
Thresholds:
Eradication strategies:
In large dense stands a hot fire may be used to kill old shrubs and encourage seed to germinate so that it may controlled by herbicides and reduce the soil seed bank.
Cutting at the base, ringbarking or bulldozing and hand pulling seedlings provides good control.
For mature or juvenile shrubs, apply a mixture of 1 L of Grazon in 100 L of water to the foliage.
For seedlings, apply 4 L/ha of glyphosate (450 g/L) or spray until just wet with a mixture of 100 mL of glyphosate (450 g/L) per 10 L of water.
For juvenile shrubs, spray a mixture of 100 mL of glyphosate (450 g/L) plus 25 mL Pulse Penetrant per 10 L of water onto the foliage until just wet. A concentrated mix of 1 part glyphosate with 2 parts water can also be applied using a window washer bottle. Apply about 3 mL of this solution per square metre of foliage. Lontrel®750 at 2 kg/ha may provide more selective control in some situations.
A basal bark treatment is often the most cost effective using a mixture of 1 L of Access® in 60 L of diesel applied to the lower 50 cm of the trunk and repeated in 6 months if necessary.
Good control can also be achieved by injecting the stems with 1 mL Tordon® Timber Control herbicide per 1.5 metres of height in autumn or spring when trees are actively growing.
Repeat the treatment every second year to ensure that no plants reach an age where they can set seed.
A large number of seedlings often emerge in the season after felling, burning or spraying. If these are left the infestation may become worse. Follow up every 2-3 years to ensure no trees reach an age where they set seed.
If glyphosate is not providing good control then try Garlon®, Grazon®, Hotshot®, Starane® or clopyralid(300g/L). Test various times of treatment in your area. Avoid further burning or denuding of the area as this will encourage seedling establishment.
Don't buy or plant them in gardens outside of their native range which was Queensland and Northern NSW.
Herbicide resistance:
None reported
Biological Control:
Unlikely because many are Australian native species.
Related plants:
See A key for weedy Acacias and similar native species
There are more than 500 native Acacia species in WA.
Weedy and look-alike species include
Acacia Hedge (Acacia paradoxa). Noxious weed.
Black Wattle (Acacia decurrens) Bark used for tanning.
Blackwood (Acacia melanoxylon) Bark used in tanning.
Blakely's Wattle (Acacia blakelyi) Used in revegetation.
Brigalow (Acacia harpophylla)
Burrow's Wattle (Acacia burrowii)
Caterpillar Wattle (Acacia lasiocalyx) Used in revegetation.
Georgina Gidgee (Acacia georginae) is toxic to stock.
Golden Wattle (Acacia pycnantha)
Golden-wreath Wattle (Acacia saligna) Used in revegetation.
Gosford Wattle (Acacia prominens) Ornamental
Green Wattle (Acacia mearnsii) Bark used in tanning.
Hop Mulga (Acacia craspedocarpa)
Manna Wattle (Acacia microbotrya) Used in revegetation.
Mimosa bush (Acacia farnesiana)
Motherumbah (Acacia cheelii)
Mountain Cedar Wattle (Acacia elata)
Mulga (Acacia aneura) Used for fodder.
Prickly Acacia (Acacia nilotica). Noxious weed.
Prickly Moses (Acacia pulchella)
Queensland Silver Wattle (Acacia podalyriifolia)
Red Wattle (Acacia sylvestris)
Silver Wattle (Acacia dealbata)
Snowy River Wattle (Acacia boormanii) Ornamental
Sweet Wattle (Acacia suaveolens)
Sydney Golden Wattle (Acacia longifolia)
White Sally (Acacia floribunda)
Acacia glaucescens is toxic to stock.
Acacia jucunda
Racosperma species.
Plants of similar appearance:
Acacia jucunda is very similar but has narrower phyllodes, shorter hairs and a more prominent gland.
References:
Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).
Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).
Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume 2. P379. Diagram.
Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (2007). Western Weeds. A guide to the weeds of Western Australia. (Second Edition). Plant Protection Society of Western Australia, Perth, Western Australia. P192. Photo.
Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #3.20.
Maslin, B.R. (2001) Wattle. Acacias of Australia. CD.
Moore, J.H. and Wheeler, J.R. (2008). Southern Weeds and their Control. (Second Edition). Department of Agriculture and Food Western Australia. P171. Photos.
Paczkowska, G. and Chapman, A. (2000). The Western Australia flora: a descriptive catalogue. (Wildflower Society of Western Australia (Inc), the Western Australian Herbarium, CALM and the Botanic Gardens & Parks Authority). P319.
Wheeler, Judy, Marchant, Neville and Lewington, Margaret. (2002). Flora of the South West: Bunbury - Augusta - Denmark. (Western Australian Herbarium, Bentley, Western Australia). P674. Diagram.
Acknowledgments:
Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.
